1. Field of the Invention
This invention relates to aircraft control under emergency conditions, and more particularly to aircraft control by means of lateral fuel transfer and engine thrust control acting in tandem to provide aircraft navigational control.
2. Description of the Related Art
Aircraft, particularly large commercial aircraft carrying hundreds of passengers over global distances, are similar to any aircraft in their use of flight control surfaces to navigationally control the craft. These control surfaces include the ailerons on the wings as well as the elevators and rudders present in the tail section. Engines are usually distributed underneath each wing, either alone or in pairs, and for some aircraft the vertical stabilizer also includes a tail engine. Fuel sufficient for long journeys (with the cargo and personnel loads involved) may be distributed throughout the aircraft in the wings and the cargo sections of the craft. In order to effect control over the fuel and to allocate weight within the aircraft, lateral fuel transfer between individual fuel tanks is well known and occurs often. By providing control over lateral fuel transfer between individual fuel tanks, fuel weight and space can be allocated and controlled within the confines of the airframe.
Occasionally, and although redundant systems are designed and implemented to work against such occurrences, emergency conditions arise where absolute and total failure of control over all control surfaces arises. This was the case with United Airlines Flight 232 when it suffered a complete loss of all three redundant hydraulic systems on Jul. 19, 1989 due to structural failure in the tail engine. The pilots had only control over thrust in the remaining two engines in order to guide the plane into Sioux City, Iowa. Although many lives were saved, many lives were also lost in the crash landing of the aircraft.
United Airlines Flight 232 relied on throttle controls of engines No. 1 and No. 3, the two wing engines, to provide navigational control of the aircraft. However, had one of the wing engines also gone out in conjunction with the tail engine, that would have left only a single engine with which to fly the plane. While it is possible to fly a commercial airplane with only one engine, without the use of hydraulic controls, and without the use of center of gravity control, the task becomes impossible. It is possible that under emergency conditions, such single engine flight control must be effected without the use of hydraulic controls. Under such circumstances, it becomes necessary (possibly leading to a greater rate of survival) to augment control by altering the center of gravity of the aircraft by shifting the location of the fuel within the confines of the airframe. The present invention sets forth means by which such emergency control of the aircraft may be effected through one engine and lateral fuel transfer.